I was checking the oil in the diesel on our (new to us) Catalina 42 and noticed the coolant level was low in the plastic coolant reservior. we have a Yanmar 48 H.P 4JH2. do not see any sign of leaks so I think it just low. ? can I use automotive type anti-freeze like Prestone in this cooling system or do I have to use a marine type.
Thanks for any help on this

DO NOT USE REGULAR AUTOMOTIVE ANTIFREEZE. I took the Yanmar Deisel Maintenance course last year and they stressed over and over and over, NEVER use regular automotive anti-freeze. They recommend EVANS Anti-Freeze as the best.

We tore down a Yanmar that had overheated with regular auto anti-freeze. Trust me, you don''t want the inside of your engine looking like that!!

Also, I think what you refer to as the "plastic coolant reservoir" is actually the coolant expansion tank (fresh water sub tank). The level in this tank is NOT an indication of your coolant level within the system.

I think the "plastic coolant reservoir" of which you speak is actually the overflow, no? On the engine itself shud be a radiator cap similar to what you might find on a car. Open that by following the directions printed on it and check the coolant level that way. Also, as for using Evans or whatever; most engine manufacturers recommend NOT mixing different types of coolants. IE if Brand X is in there, continue to use it. Also, full strength anti-freeze needs to be cut down by 1/2 with water generally. IE what you add to the engine is 50% antifreeze/50% pure water. Do yourself a HUGE favor and get the manual on your engine; it will address this and other issues such as oil type, oil & fuel filters, air filters, and, most importantly, how to change your raw water impeller which you shud do every year.

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